1 2 Antibacterial actions of silver nanoparticles incorporated Zn–Al layered double 3 hydroxide and its spinel 4 Geetanjali Mishra Q1 , Barsha Dash *, Sony Pandey, Prangya Paramita Mohanty 5 CSIR-Institute of Minerals and materials Technology, Bhubaneswar 751013, Orissa, India 6 7 Introduction 8 Silver, zinc and copper are found to be having excellent 9 antibacterial activity. This property of the elements is exploited by 10 incorporating them in different kind of materials like fibers, [1] 11 ceramics [2] and coatings [3] etc. But the effectiveness of the 12 antibacterial property lies in the homogenization and well 13 dispersibility of the metals [4]. The dispersibilities of the metals 14 and their ions are at ease in coprecipitation system for synthesizing 15 a ceramic material. Antibacterial ceramic materials are predomi- 16 nantly prepared with silver incorporations [5,6]. However Zn and 17 Cu also show comparable antibacterial activity. Calamine is a 18 century old antiseptic material containing ZnO/Zn(CO) 3. Inspired 19 by this fact if a material containing above elements would be 20 prepared it is expected to show antimicrobial activity. Several 21 other studies are there for the preparation of antimicrobial 22 materials from different compounds like silver incorporated glaze 23 layers for ceramics [7], silver doped phosphate glass [8], ZnO 24 [9,10], zinc oxide/iron oxide nano composite [11]. A few 25 antibacterial materials are prepared from layered double hydro- 26 xides like polycaprolactone film with layered double hydroxide 27 (LDH) and benzoate derivatives [12], green pesticides with layered 28 double hydroxide (LDH) hybridized with cinnamic acid [13] and 29 antibacterial drug carrier [14]. 30 Layered double hydroxides are the class of materials having 31 special features of two subsequent layers of two different 32 hydroxides separated some distance apart. The layered double 33 hydroxides (LDH), also known as synthetic clays are compounds 34 where a fraction of the cationic sites are occupied by trivalent 35 cations, which causes an excess positive charge neutralized by the 36 presence of additional anion in the interlayer space. Incorporation 37 of silver nanoparticles which itself is antimicrobial results in 38 formation of an antimicrobial hybrid material. So many different 39 methods are opted for silver deposition into layered double 40 hydroxide like pulsed laser deposition [15], mixing of layered 41 double hydroxide (LDH) with silver salt solution followed by 42 reduction resulting in deposition of silver nanoparticles on the 43 surface [16]. Sometimes it is core-shell type material with silver 44 core and layered double hydroxide (LDH) shell [17] or it is biogenic 45 silver nanoparticles hybridized with layered double hydroxide 46 (LDH) gel to form a silver LDH hybrid material [18]. In all these 47 processes silver nanoparticles get deposited on the surface of the 48 layers. In order to intercalate silver between layers; first 49 intercalation should be thiosulfate which reacts with silver ion. 50 Silver forms a linear complex with the two sulfur atoms of the 51 interlayer thiosulfate [19,20]. 52 Very few researches have been done in the field of antibacterial 53 ceramic material preparation using layered double hydroxide. 54 Antimicrobial ceramics are the considerable materials to go 55 beyond health care to bathrooms and kitchens. Disinfectant floor 56 cleaners generally kill the bacteria from the surface but can not 57 protect the surface from contamination. Whereas antimicrobial 58 ceramics can give continuous protection against bacteria and Journal of Environmental Chemical Engineering xxx (2013) xxx–xxx A R T I C L E I N F O Article history: Received 3 June 2013 Received in revised form 23 August 2013 Accepted 23 August 2013 Keywords: Layered double hydroxide Antibacterial activity Silver nanoparticle A B S T R A C T Simple processes to produce silver nanoparticles deposited layered double hydroxide (LDH) and its spinels are reported. Pristine layered double hydroxide (LDH) and Ag-layered double hydroxide (LDH) composite are synthesized through co-precipitation followed by ageing at 150 8C. The aforementioned composite was calcined at 800 8C to produce the corresponding spinel combined with Ag 2 O. Both of the composite and the calcined product are found to be showing antibacterial activity but sporulation in the fungal activity. The zone diameters of Ag-layered double hydroxide (LDH) composite are 5 mm and 6 mm for Escherichia coli and Staphylococcus aureus whereas the same for calcined Ag-layered double hydroxide (LDH) are 15 mm and 18 mm for the same bacteria showing stronger antibacterial activity of the calcined product over the composite itself. This result may lead to its application in ceramic industries. ß 2013 Published by Elsevier Ltd. * Corresponding author. Tel.: +91 674 2379325. E-mail address: barsha.dash@gmail.com (B. Dash). G Model JECE 145 1–7 Please cite this article in press as: G. Mishra, et al., Antibacterial actions of silver nanoparticles incorporated Zn–Al layered double hydroxide and its spinel, J. Environ. Chem. Eng. (2013), http://dx.doi.org/10.1016/j.jece.2013.08.031 Contents lists available at ScienceDirect Journal of Environmental Chemical Engineering jou r n al h o mep ag e: w ww .elsevier .co m /loc ate/jec e 2213-3437/$ – see front matter ß 2013 Published by Elsevier Ltd. http://dx.doi.org/10.1016/j.jece.2013.08.031